Wireless data transmission is a rapidly growing field. One increasingly popular form of such transmission is wireless local areas networks (WLANs). A number of standards currently exist for WLANs. However, they tend to be fragmented and largely incompatible. There is a desire for a worldwide standard that would allow a single device to function virtually anywhere in the world providing high-speed connectivity.
WLANs require specific protocols to transmit information, as do wired LANs. With numerous stations along a network, LAN stations must take care to prevent collisions if more than one station wishes to transmit information in the LAN. The situation is more critical in the wireless environment (i.e., WLANs) since wireless stations and wireless access points behave differently from wired stations.
Recently, bands have opened up between 5 and 6 GHz, which may permit a worldwide standard. Wireless standards are being developed to utilize those bands. One such standard is HIPERLAN/2 (High Performance Radio Local Area Network Type 2), which is of European origin. Another such standard is IEEE 802.11a, which originates primarily in the US. Japan is developing standards similar to both those in the US and Europe. Both the US and European standards profess similar levels of performance, and use very similar waveforms to communicate. However, the two standards are currently incompatible. Particularly at the Media Access Control (MAC) layer. As such, a large push has developed to create a single hybrid standard, or provide some means for the two standards to easily interoperate.
Many situations occur where 802.11a WLANs must substantially coexist with HIPERLAN WLANs. Since they operate at overlapping frequencies, contention collisions are frequent and must be resolved if the two systems are to operate without interference in close proximity to each other.
Methods for interoperation of HIPERLAN and 802.11a systems are being contemplated in which systems conforming to both standards might share one common channel without interference. A super-frame structure has been proposed to support interoperation between the standards. The proposed structure contemplates a super frame with an 802.11 phase and a HIPERLAN/2 phase (See super-frame structure shown in FIG. 3). The super frame has a length of 2 k×2 ms, where k is an integer. Duration of the 802.11 beacon plus the 802.11a phase is set at n×2 ms. The HIPERLAN/2 phase comprises m×2 ms. The sum of m and n would be 2k.
This method of facilitating interoperability of HIPERLAN and 802.11a has some drawbacks. For one, this approach presumes that the 802.11 terminals can be prevented from transmitting during the HIPERLAN operating phase. Currently, no mechanism exists within the 802.11 standard to allow this. Also, the problem is best addressed by a solution compatible with existing generations of terminals.